My FRiend I must have a stack of old Brownell catalogs a couple of feet high by now, my main source of parts and illustrations. Being a hobbyist gunsmith and machinist I have concepts of assault rifles and battle rifles that will be on my workbench in the future.
Its when you get into the small precision engineered plastics is where you can make money or being able to make molds for castings. And castings are very important, its a long bit of labor to machine something by hand, harder yet to duplicate that without a CAD CNC mill.
Definitely worth investing into because I have a feeling Obama will try to regulate these 3D machines severely.